Mort J S, Recklies A D, Poole A R
Arthritis Rheum. 1984 May;27(5):509-15. doi: 10.1002/art.1780270505.
The presence of the lysosomal proteinases cathepsin B and cathepsin D at extracellular sites in rheumatoid synovium was demonstrated using the antibody capture technique. Unlike cathepsin D, the cysteine proteinase cathepsin B was commonly detected only at the edges of the synovial explants. Radioimmunoassay and enzyme activity assay of these proteinases demonstrated that both were released from rheumatoid synovial cells in comparable amounts. Since lysosomal cathepsin B is unstable and denatured at physiologic pH and the antibody used only recognizes inactivated enzyme, we believe the selective detection of cathepsin B at the edge of the synovium may be due to the proteinase maintaining a native conformation within the explant, where the pH may be low enough to permit this. By use of a fluorescent substrate in a sensitive, continuous enzyme assay, cathepsin B was shown to express significant activity at neutral and alkaline pH before being inactivated. This and earlier work from this laboratory indicate that cathepsin B secreted by rheumatoid synovial cells may possess extracellular activity in vivo and be involved in the degradation of connective tissue macromolecules.
采用抗体捕获技术证实了类风湿性滑膜炎细胞外部位存在溶酶体蛋白酶组织蛋白酶B和组织蛋白酶D。与组织蛋白酶D不同，半胱氨酸蛋白酶组织蛋白酶B通常仅在滑膜外植体边缘检测到。这些蛋白酶的放射免疫测定和酶活性测定表明，二者均以相当的量从类风湿性滑膜细胞中释放出来。由于溶酶体组织蛋白酶B在生理pH值下不稳定且会变性，且所用抗体仅识别失活的酶，我们认为在滑膜边缘选择性检测到组织蛋白酶B可能是由于该蛋白酶在外植体内保持天然构象，其pH值可能足够低以允许这种情况发生。通过在灵敏的连续酶测定中使用荧光底物，发现组织蛋白酶B在失活前在中性和碱性pH值下表现出显著活性。本实验室的这项工作以及早期工作表明，类风湿性滑膜细胞分泌的组织蛋白酶B在体内可能具有细胞外活性，并参与结缔组织大分子的降解。
